From b6345dcc9fff025c6c454608e03fb215fe1b139f Mon Sep 17 00:00:00 2001
From: "M. Mert Yildiran" <mehmet@up9.com>
Date: Tue, 14 Jun 2022 11:23:13 +0300
Subject: [PATCH] Fix `go_crypto_tls_ex_uprobe`

---
 tap/tlstapper/bpf/go_uprobes.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tap/tlstapper/bpf/go_uprobes.c b/tap/tlstapper/bpf/go_uprobes.c
index aff9a8fca..a7bc6dde9 100644
--- a/tap/tlstapper/bpf/go_uprobes.c
+++ b/tap/tlstapper/bpf/go_uprobes.c
@@ -132,6 +132,15 @@ static __always_inline void go_crypto_tls_ex_uprobe(struct pt_regs *ctx, struct
         return;
     }
 
+    // In case of read, the length is determined on return
+    if (flags == FLAGS_IS_READ_BIT) {
+        info.buffer_len = GO_ABI_INTERNAL_PT_REGS_R1(ctx); // n in return n, nil
+        // This check achieves ignoring 0 length reads (the reads result with an error)
+        if (info.buffer_len == 0) {
+            return;
+        }
+    }
+
     output_ssl_chunk(ctx, &info, info.buffer_len, pid_tgid, flags);
 
     return;